Engine revs when on idle

for some reason when my car is just sitting & running (basically in park) the engine starts to rev up about 5oo rpm's...i think its a vacum leak, but im not to sure...any got any sugestions

Could be a vaccum leak, could be a whole lotta things. Could even be your throttle cable expanding when hot. If you blip the throttle, will it go back down?

Sounds like ya have an automatic (park)? It could be due to a PCM problem. The cars computer could be compensating for a sensor fault. I read about a problem much the same a while ago... The problem was the O² sensor.

Try getting your PCM scanned, should give you an indication of what sensors are faulty. (if any)

i cant scan my computer cuz i need an engine swap so the computer wont be able to pick up the right codes...plus i checked that already and the scanner just doenst do anything, but thanks tho, im leaning my towards a vaccum leak.......

just got my car back today over this. my fuel injection controller and a few spark plugs were dead. let's go team. could also easily be a vacuum leak. PCB valve could be clogged (can cause problems on some cars) O2 sensor could be fubared, anything dealing with fuel injection, spark plugs, etc.

First off, what kind of car is it?